1. Field of the Invention
This invention relates to apparatus for providing high availability of workstations in a computer system and more particularly, to workstation takeover control apparatus in a high availability computer system including a primary host computer, a primary or controlling workstation controller, a plurality of workstations, a secondary host or standby computer, and a secondary workstation controller.
The invention finds particular utility in a computer system which requires backup over workstations and workload of the computer system.
2. Description of the Prior Art
The prior art such as U.S. Pat. Nos. 3,303,474; 3,593,302 and 3,864,670 is directed to an arrangement where a common piece of hardware monitors operation and detects errors in one of the computers and switches to the operable computer. In the present invention there is no single element in the data path that is subject to failure. The monitoring functions are in each system so that most single failures are prevented from making the entire system inoperable. In the present invention, a secondary or standby workstation controller is connected to appear to the primary or controlling workstation controller as a workstation in a manner to eliminate the need to change the interconnections by taking advantage of the cable-through feature when the secondary workstation controller is caused to function as a workstation controller upon the failure of the primary workstation controller. The secondary workstation controller's driver resistors are connected to function as terminators but can also function as driver resistors when the secondary workstation controller functions as a workstation controller, i.e., becomes the primary workstation controller.